Navigation Links
Why chromosomes never tie their shoelaces

In the latest issue of the journal Nature, Miguel Godinho Ferreira, Principal Investigator at the Instituto Gulbenkian de Cincia (IGC) in Portugal, lead a team of researchers to shed light on a paradox that has puzzled biologists since the discovery of telomeres, the protective tips of chromosomes: while broken chromosome ends generated by DNA damage (such as radiation or cigarette smoke) are quickly joined together, telomeres are never tied to each other, thus allowing for the correct segregation of the genetic material into all cells in our body. Since telomeres erode in response to the continuous cell divisions in our body, this protective function fades away as we grow older. Complete loss of telomeres results in sticky chromosome-ends that join to each other creating to genetic chaos the very initial steps of cancer. Understanding how the tips of the chromosomes are protected from DNA repair and how the cells respond when they are unprotected will provide insights into the initial stages of tumourgenesis, ageing and future therapeutic interventions.

Cells respond to broken or damaged DNA by arresting their cell cycle while the damage is repaired. If the tips of chromosomes were recognized as broken DNA, cells would be constantly trying to mend the ends of chromosomes, leading to cell death and mutations in the DNA. Telomeres - the caps made up of protein and DNA at the tips of chromosomes - stop this from happening.

Through a series of meticulous experiments the Portuguese team, in collaboration with researchers at University of Illinois, Chicago, reveal that the crux lies in the changes of a protein, a Histone modification, located close to the telomeres. Histones are found along the entire length of all chromosomes, helping to package the DNA and also playing a role in regulating gene activity. Using fission yeast (used to make bread and beer) as a model organism, the researchers found that one of the Histones neighbouring the telomeres lacks a chemical signal, thus rendering the DNA damage recognition machinery incapable of arresting the cell cycle.

Says Miguel Godinho Ferreira, 'It's amazing, but it appears to be this single change that underlies the cell's ability to distinguish the end of the chromosome (i.e. a telomere) from a break in the middle. Indeed, along the rest of the genome, these Histones retain the chemical signal, so that when DNA damage does occur in any of these regions, DNA repair is set up and broken ends joined together.'

Telomeres are like the plastic caps on shoelaces: just as a shoelace starts unravelling when the cap is lost, so chromosome ends would become shorter with each cell division were it not for the telomeres. Telomeres are added or elongated by the enzyme telomerase. However, most cells in our body lack telomerase from when we are born, consequently telomeres become shorter and lose protection, sending signals for cells to stop dividing and start ageing. In about 85% of cancers, cells re-activate telomerase, contributing to their ability to divide and proliferate.

Even though DNA repair must be prevented at telomeres, assembly of the DNA damage recognition machinery is vital for telomerase activation and telomere elongation. Miguel Godinho Ferreira adds, 'Eukaryotic cells have evolved a very specific mechanism whereby telomerase recruitment goes ahead undisturbed, yet the whole DNA repair process is kept at bay from chromosome ends. Knowing the details of telomere capping is crucial to understanding its relationship to cancer, ageing and several diseases, and the multiple ways in which telomere manipulation may, potentially, lead to effective treatments".

He continues emphasizing the importance of fundamental basic research: "When Liz Blackburn, Carol Greider and Jack Szostak discovered telomerase and telomeres in the 80s, for which they got last year's Nobel Prize in Physiology or Medicine, they were searching for a solution to the "end-replication problem" and far from imagining the clinical implications these findings are currently developing. They were simply solving an academic puzzle created by the discovery of the double helix and the inability of DNA polymerases to synthesize the ends of linear DNA. Likewise, we are honored and excited to contribute to unravel these mechanisms, but perfectly aware that the direct implications of this work are still many years away".


Contact: Silvia Castro
Instituto Gulbenkian de Ciencia

Related medicine news :

1. Infectious Virus Hides In Human Chromosomes During Latency And Can Be Passed From Parents To Their Children
2. Womens Chromosomes May Affect Blood Pressure
3. Enterprise PDM Integration has Never Been Easier; Zero Wait-State Announces Leading SolidWorks Reseller GoEngineer as Master Distributor for DesignState
4. Gene is linked to lung cancer development in never-smokers
5. Business Book Author is Breaking All the Rules and Utilizing Social Media in a Way that Has Never Been Done Before
6. Ross Nanotechnology Corporation Introduces the NeverWet™ Coating on its First Consumer Product – The Clear-n-Clean Plunger
7. Global Basecamps Launches New Website: Researching and Booking Sustainable Travel Has Never Been Easier
8. Revolutionary Sports Bottle Unscrews at Both Ends for Easy Cleaning -- Never Deal With Stinky, Moldy Bottles Again
9. 1 in 4 Californian children have never seen a dentist, study finds
10. Phonak Asks Young FM Users to Tell Their Stories on YouTube
11. Luth Researchs IndicatorEDG(TM) Study Finds Americans Hopes of Achieving Their Dreams Are Fading
Post Your Comments:
Related Image:
Why chromosomes never tie their shoelaces
(Date:11/24/2015)... UT (PRWEB) , ... November 24, 2015 , ... It ... Magazine. For a business, it is critical that the first impression be positive and ... they are not likely to buy anything or want to return. They will also ...
(Date:11/24/2015)... ... November 24, 2015 , ... ... their knowledge and experiences at a live taping of the next CURE ... the Cure of Gastrointestinal Cancers 2015 Symposium at Georgetown University Hotel & Conference ...
(Date:11/24/2015)... ... ... Aided by seed funding from the Ron Foley Foundation, researchers at Western ... how to detect and treat pancreatic cancer (PC). , WCHN researchers will focus ... (ncRNA), genetic material that is present in the blood of patients with PC. ...
(Date:11/24/2015)... ... November 24, 2015 , ... ... its exceptional customer service: the TrustDale certification. The award recognizes good companies for ... stone honing , tile and grout, and hard surface restoration company earned this ...
(Date:11/24/2015)... ... November 24, 2015 , ... World Patent Marketing ... a household invention that revolutionizes the vending machine industry by providing healthy and ... worth $2 billion," says Scott Cooper, CEO and Creative Director of World Patent ...
Breaking Medicine News(10 mins):
(Date:11/24/2015)... , Nov. 24, 2015  Boston Scientific Corporation (NYSE: ... Oppenheimer 26th Annual Healthcare Conference on December 8, in ... Susie Lisa , vice president, Investor Relations, will participate ... beginning at approximately 8:35 a.m. ET. --> ... in a 30-minute question-and-answer session with the host analyst ...
(Date:11/24/2015)...   Renowned UAE ... s advice and insights on supplements and healthy diet ... 50% of Dubai residents are not ...   femMED launches comprehensive solutions for women , ... residents are not consuming enough to keep themselves healthy. A local ...
(Date:11/24/2015)... 2015 Abaxis, Inc. (NasdaqGS: ABAX ), ... for the medical, research, and veterinary markets worldwide, announced ... will present at the 27 th Annual Piper ... 11:30 a.m. ET. The conference will be held at ... York City . Abaxis, Inc. is ...
Breaking Medicine Technology: